Chronic pain is the expression of a neurological disease state that manifests as increased excitability of dorsal horn neurons in the spinal cord known as central sensitization. NMDA receptors play a pivotal role in development and maintenance of central sensitization. Recent evidence supports an inhibitory effect of local anesthetics on NMDA receptors, however, little is known as to the mechanism by which this inhibition occurs. This project will evaluate the mechanism by which bupivacaine and lidocaine, two amide local anesthetics widely used in clinical practice inhibit NMDA receptor currents. Aim 1 will determine dose-response relationships in recombinant receptors focusing on the main isoforms expressed in dorsal horn neurons. Aim 2 will investigate the mechanism of inhibition with single-channel recordings, kinetic modeling and computational stimulation. Aim 3 will explore the structural domain determinants involved in sensitivity to anesthetics, and how these translate local anesthetics' inhibitory mechanism. Results from this project will increase understanding of pharmacologic strategies to prevent or ameliorate central sensitization and possible treatment and prevention of chronic pain by using local anesthetics.